Hackney is at risk of losing one of its MPs when the next election comes around, if fears are borne out that a quarter of the electorate is wiped off the voting register on December 1.

Every voter in the borough is being urged to double check they are registered to vote by November 20, because of sweeping Cabinet Office constitutional reforms.

The Electoral Commission had recommended a year’s delay to the changes but a vote in the House of Lords last week, defeated by just 11 votes, means the changes take place imminently.

Previously, the head of the household could register everyone living at the address. But to tackle fraud, everyone must now register personally – and few people are aware of the changes.

Nationally, four per cent of voters will lose their vote on average – but Hackney is expected to be the worst hit borough in the country, losing 23 per cent.

Constituencies have traditionally been based on geographical areas. But the government has decided to change this and base the need for an MP on the number of registered voters in an area, slashing the number of MPs from 650 to 600.

Thus the voting registration figures will be used as the basis for electoral boundary change, and it is feared that the knock-on effect of 23 per cent of voters being struck off the register could be the loss of one of Hackney’s two MPs at the next election - currently Meg Hillier for Hackney South and Shoreditch and Diane Abbott for Hackney North and Stoke Newington.

John Page, speaking on behalf of political campaign groups Hope Not Hate and Hackney Unites, said: “This is a crisis of democracy.

“Unless we act now, this will have the immediate withdrawal of 44,000 people from the register in Hackney, the vast majority of whom have the right to vote but will be deprived of a vote when it comes to the London Mayoral and Assembly elections in May.

“As if that wasn’t bad enough the government intends to redraw the constituency boundaries based on this undercounting – it is very hard to see how Hackney will continue to have two MPs following the Boundary Commission’s report, given the substantial undercounting of Hackney voters.

“Hackney has lots of issues that need to be raised in Parliament, it is experiencing transformation and the people of Hackney need a voice. If that’s reduced, it’s not good news for democracy or the people of Hackney.

“Because of the way this disproportionately impacts on urban areas, Hackney is the worst affected area in the country, it’s the combination of the at-risk groups – people who move regularly, young people, a significant ethnic population, all of those combined.

“The vast majority of those people who are going to have their names taken off will assume they can vote as they were able to vote in the last elections in May. What’s likely to happen is people turn up to vote in May and are turned away from the polling booth.”

He urged everyone to check whether they are registered and to speak to friends and neighbours.

Individuals can still register to vote after November 20, but they will not be taken into account for the redrawing of boundaries.

The Cabinet Office declined to comment.

See gov.uk/register-to-vote to register, or phone: 020 8356 3000 and ask to register to vote. Otherwise register in person at the Hackney Service Centre in Hillman Street, behind the Town Hall from Monday to Friday 9am to 5pm.